Antuco (37.4°S, 71.4°W; Chile) is a dominantly basaltic stratovolcano whose original?~?3300 m altitude main cone experienced a catastrophic sector collapse at?~?7.1 cal ka BP, producing a volcanic debris avalanche deposit (VDAD) with hummocky surface and?~?6.4 km3 of volume. We carried out geological studies of its debris avalanche deposit, which was distributed to the W and displays a longitudinal facies transformation from edifice’s megablocks and block to mixed facies in distal areas (up to 25 km from the scar). Our observations support the behavior of the avalanche beginning as a translational slide, and then as plug flow when confined within the Laja River valley. Clay abundance and high content of hydrothermally altered material may suggest active participation of water; flow velocities are estimated to?~100 m s?1. We primarily identify the steep-sided flanks of the cone, and hydrothermal alteration promoted the edifice instability, while basement seismogenic structures may have ultimately triggered the landslide. Subsequent landslide-led events include the transformation of the volcanic activity with explosive eruptions producing a sequence of dilute pyroclastic density currents (PDCs) ending?~3.4 ky BP, and extensive lava effusion rapidly reconstructing the collapsed edifice. Moreover, the Antuco VDAD also blocked the natural output of the Laja Lake, increasing its level by?~200 m and then triggering cataclysmic outburst floods by dam rupture, preserved as high-energy alluvial beds with ages between 2.8 and 1.7 ky BP. The Antuco constitutes an excellent example of a critical chain of events initiated by a stratovolcano lateral collapse and warns for detailed hazard investigations to better comprehend its related impacts.
This paper examines community-based water supply management (CBWSM) in three rural districts of Northwest Cameroon as well as a review of the literature focusing on some successful community-based natural resource management initiatives in sub-Saharan Africa. Using empirical and secondary data collected through participatory research methods, it is argued that CBWSM has failed to achieve sustainable water supplies in Northwest Cameroon. Findings revealed that centralized control, the prevalence of poverty, passive involvement of public, private and grassroots community has continued to thwart water supplies within these districts. It is important to note that in any natural resource management system, power becomes a crucial factor as it determines who has and does not have access to common-pool resources. This paper argues that argues that strong traditional leadership, resolute devolution, and active participation of rural communities will facilitate and invigorate a platform for capturing the views of diverse user groups and this can bring about a people-centered and community-driven development process. Some aspects of best practice arising from successful case studies in Cameroon can contribute significantly to promoting the development of effective CBWSM in other rural communities with similar characteristics in and out of Cameroon. This will be possible only if rural groups are involved and engaged in the management of their resources while integrating some aspects of best practice.
We present the design of a novel way of handling astronomical catalogs in Astro-WISE in order to achieve the scalability required for the data produced by large scale surveys. A high level of automation and abstraction is achieved in order to facilitate interoperation with visualization software for interactive exploration. At the same time flexibility in processing is enhanced and data is shared implicitly between scientists. This is accomplished by using a data model that primarily stores how catalogs are derived; the contents of the catalogs are only created when necessary and stored only when beneficial for performance. Discovery of existing catalogs and creation of new catalogs is done through the same process by directly requesting the final set of sources (astronomical objects) and attributes (physical properties) that is required, for example from within visualization software. New catalogs are automatically created to provide attributes of sources for which no suitable existing catalogs can be found. These catalogs are defined to contain the new attributes on the largest set of sources the calculation of the attributes is applicable to, facilitating reuse for future data requests. Subsequently, only those parts of the catalogs that are required for the requested end product are actually processed, ensuring scalability. The presented mechanisms primarily determine which catalogs are created and what data has to be processed and stored: the actual processing and storage itself is left to existing functionality of the underlying information system. 相似文献
Annually resolved and replicated tree-ring stable isotope series have the potential to reconstruct growing season environmental parameters over multi-millennial timescales. As this archive may require only minimal statistical detrending, it has the potential to preserve a large portion of low frequency climate signals. To date, many studies have utilised only the latewood portion of the tree ring, in an attempt to minimize carry-over effects from previous year reserves and maximise the annual nature of the climate signal preserved. However, the old trees from tree-line locations, necessary to build long chronologies, often display narrow ring-widths (< 0.5 mm), making accurate earlywood–latewood separation difficult and particular time consuming. The resulting samples may also be too small for efficient cellulose purification or multiple isotopic determinations. As photosynthates from the current year are predominantly used in conifer ring formation at marginal sites with short growing seasons, latewood separation may not be especially advantageous in determining a useful climate signal and therefore unnecessary where resources are limited. To test this hypothesis, Scots pine from Northern Norway and European larch from the Swiss Alps are used. Both sites are tree-line locations where growth is predominantly temperature limited. Tree rings were cut and extracted to cellulose for both the earlywood and latewood of each annual growth ring and stable carbon isotope ratios were measured. Our results demonstrate a very high common carbon isotope signal between earlywood and latewood in both species (rlarch = 0.68 and rpine = 0.79), which also show high correlations with summer temperature over the investigated period (AD 1980–2004 for larch and AD 1929–1978 for pine). High turnover rates and small reserve pools at these tree-line locations may account for these high common signals. These results suggest that for European tree-line conifers, the separation of earlywood from latewood is unnecessary to resolve an annual isotopic signal and make a reliable climate calibration. Using the whole ring may provide additional analytical advantages and consequently even improve climate calibrations. 相似文献
The aim of this paper is to present a preliminary analysis of unitary authority level data from the 2001 census of population on the spatial (and, where available, temporal) patterns in proportions of Welsh speakers in Wales. In so doing we draw attention to the advantages (and limitations) of the census as a source of information on the state of the Welsh language. Although a 2 per cent increase in the percentage of Welsh speakers between 1991 and 2001 has been welcomed, several commentators have drawn attention to the change in the nature of the question asked at the 2001 census which may account for some of this increase. In this paper, we assess what is, and is not, possible to discern from the census, draw attention to other potential sources of information on the language and make some preliminary recommendations for those agencies concerned with monitoring trends in the future, both with regard to the need for more detailed language use surveys and the nature of the question included in subsequent censuses that would permit a more useful comparison of spatial and temporal trends. 相似文献